An image sensor is a semiconductor device for converting an optical image into an electrical signal. An image sensor typically includes a light sensing region that senses light and a logic circuit portion which processes the sensed light into the electrical signal to make it data.
In general, a complementary metal oxide semiconductor (CMOS) image sensor includes a photodiode and a MOS transistor in each pixel and makes use of a switching scheme detecting outputs using the photodiode and transistor.
Often, a factor tending to degrade the performance of a CMOS image sensor is a hot pixel. To attempt to solve the problem of a hot pixel, a metal layer is sometimes deposited in a predetermined region of a pixel array to form a light blocking region, and the hot pixel is removed by analyzing the signal of the light blocking region and a light receiving region.
However, the metal layer in the light blocking region is formed on a final metal wiring layer, thereby causing a crack in the device due to stress in a subsequent process. Thus, there exists a need in the art for an improved image sensor and manufacturing method thereof.